1. Field of the Invention
A safe-geometry pneumatic nuclear fuel powder blender.
2. Description of the Prior Art
In the fabrication of nuclear fuel it is necessary to blend large volumes of powders containing fissile material. A geometrically favorable equipment design can be employed for the blending chamber to prevent accumulation of a critical mass of the fissile material during the blending operation. One geometrically favorable design is a narrow rectangular tank, referred to as a "slab tank", as disclosed in U.S. Pat. No. 3,746,312 of Hans Pirk, for example, which exemplifies a relatively high degree of simplicity. Such a slab tank may range in thickness from about two-and-one-half inches to about seven-and-one-half inches, depending upon the type and concentration of fissile material being blended. The FIG. 3 version of the Pirk slab tank blender is described as being air operated to obtain a fluidized bed having upward and downward moving components arrived at by variable automatic preselected discharges from spaced-apart sites in a porous bottom member of the slab tank. Under not uncommon circumstances, however, the fissile material powder particles to be blended may be of such degree of fineness that the establishment of the counterflowing fluidized bed action relied on for the powder blending becomes difficult if not impossible to obtain, irrespective of tank width, and the technique becomes limited to blending of heavier powders, capable of fluidized bed action. At large tank widths to handle larger powder volumes, eight feet for example, excessive blending time and complex wall stiffening structures are required.